<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
<div id="app">
    <button @click="changeToB">changeToB</button>
    <component :is="currentComponent"></component>
</div>
<script src="https://unpkg.com/vue@2.6.14/dist/vue.js"></script>
<script>
   var vm = new Vue({
    el:'#app',
    data:{currentComponent:'component-a'},
    methods:{
        changeToB(){
            this.currentComponent = 'component-b';
        }
    },
    components:{
        'component-a':{
            template:`<div>a</div>`
        },
        'component-b':{
            template:`<div>b</div>`
        }
    }
   });
</script>
</body>
</html>